Buck Converter With Merged Active Charge-Controlled Capacitive Attenuation

This letter introduces a converter and a complementary digital controller that, compared to conventional buck, have a smaller output filter volume, improved dynamic response, and lower switching losses. To reduce the volume and switching losses, the input-to-output voltage difference is decreased with a capacitive attenuator that replaces the input filter capacitor and has approximately the same volume. Both the attenuator and the downstream buck converter share the same set of switches, minimizing conduction losses. A single digital controller governs operation of the both stages. The controller utilizes the inductor current to regulate the center tap voltage, through a charge-control algorithm. During transients, the attenuator is bypassed, so the inductor current slew rate is improved. Experiments with a 5-1.5-V, 2.5-A, 1-MHz prototype show that, compared to the conventional buck, the merged topology has 43% smaller inductor, 36% smaller output capacitor, up to 30% lower power losses, and a 25% faster transient response.